Early detection of Alzheimer’s disease using x-rays

A highly detailed x-ray imaging technique previously been used to examine tumors in breast tissue and cartilage in knee and ankle joints could used for early diagnosis of Alzheimer’s disease. Researchers at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory are the first to test the technique’s ability to visualize a class of minuscule plaques that are a hallmark feature of Alzheimer’s disease.

Scientists have long known that Alzheimer’s disease is associated with plaques - areas of dense built-up proteins in the affected brain. Many also believe that these plaques actually cause the disease. Before drug therapies that remove the plaques from the brain can be tested, researchers need a non-invasive, safe, and cost-effective way to track the plaques’ number and size.

That is no easy task as the plaques are on the micrometer scale, or one millionth of a meter. Conventional techniques such as computed tomography (CT) poorly distinguish between the plaques and other soft tissue such as cartilage or blood vessels. The new technique developed at Brookhaven, called diffraction-enhanced imaging (DEI), might provide the extra imaging power researchers crave.

DEI, which makes use of extremely bright beams of x-rays available at synchrotron sources such as Brookhaven’s National Synchrotron Light Source, is used to visualize not only bone, but also soft tissue in a way that is not possible using standard x-rays. In contrast to conventional sources, synchrotron x-ray beams are thousands of times more intense and extremely concentrated into a narrow beam. The result is typically a lower x-ray dose with a higher image quality.

In their study study, researchers from Brookhaven and Stony Brook University used DEI in a high-resolution mode called micro-computed tomography to visualize individual plaques in a mouse-brain model of Alzheimer’s disease. The results not only revealed detailed images of the plaques, but also proved that DEI can be used on whole brains to visualize a wide range of anatomical structures without the use of a contrast agent. The images are similar to those produced by high-resolution magnetic resonance imaging (MRI), with the potential to even exceed MRI pictures in resolution.

Although the radiation dose used for the study is too high to safely image individual plaques in humans, it did show that images could be produced from live animal brains to learn how the plaques grow. The ultimate goal for the researchers is to find a way to develop a safe imaging technique for humans.

The results of the study will appear in the July 2009 edition of NeuroImage.